Axsmith, Brian .
A new species of the fern Cynepteris from the Late Triassic of Arizona: Implications for the early diversification of the Schizaeales.
A new species of the Late Triassic fern Cynepteris is recognized based on a single, well-articulated specimen from the lower Chinle Formation in Petrified Forest National Park, Arizona. The specimen consists of an erect rhizome with at least ten attached fronds. The individual lanceolate fronds are up to 20 cm long and 10 cm wide at the widest point, bearing undivided pinnae up to 4 cm long with prominent midveins. The lateral veins, some of which arise from the rachis, bifurcate and anastomose producing elongate meshes. Elongate hairs occur on the rachides, veins, and abaxial lamina surfaces. Sterile and fertile fronds are identical. Numerous solitary, exindusiate sporangia occur scattered on the abaxial surfaces of the fertile pinnae. Each sporangium is ovoid to pyriform with a short, thick stalk, and a complete, apical, cap-like annulus consisting of a single row of cells surrounding a multi-cellular distal plate. The new Chinle form is the only Cynepteris with once-pinnate fronds. The species of Cynepteris are currently placed in the mono-generic family Cynepteridaceae, which clearly represents an early diverging clade of the order Schizaeales. Current molecular phylogenies estimate the divergence of this order as Late Triassic, based on constraints that recognize the Middle Jurassic genus Klukia as the oldest fossil representative. Cynepteris represents a clear Late Triassic record of the order and indicates that it diverged even earlier. Features such as reticulate venation, scattered sporangia, and lack of fertile/sterile frond dimorphism are unknown or rare in other fossil and extant members of the Schizaeales, and underscores the importance of extinct fossil clades in understanding the early divergence, morphology and biogeography of ancient plants groups like the filicalean ferns.
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1 - University of South Alabama, Biological Sciences, Life Sciences Building 124, Mobile, AL, 36688, United States
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Erie/Hilton
Date: Tuesday, July 10th, 2007
Time: 8:15 AM